Abstract
ABSTRACT Residual stresses generated by the mismatch of thermal expansion coefficients of ceramics and metals affect the strength of ceramic–metal joints. An interlayer metal can be inserted between the ceramic and metal in order to relax this stress. An analysis was carried out of the residual stresses produced during joint‐cooling and in 4‐point bending tests. The effects of interlayer thickness on ceramic–metal joint strength were then studied by considering a superimposed stress distribution of the residual stress and the bending stress. Finally, joint strength was estimated from fracture mechanics and strength probability analysis by considering the residual stress distribution, defect size and position of pre‐existing defects in the ceramic parts. As a result of this study, we suggest an optimum material selection and interlayer thickness for ceramic–metal joint structures. This approach is generally suitable for the design of electrical and mechanical structures.
Highlights
Ceramic/metal joint is an excellent technology to carry out the application expansion of the monolithic ceramics, which are brittle materials
(10~50ìm) interfacial on the ceramics side is called as IC-type fracture (IC: From the Interface neighborhood to Ceramics)
Interlayer Thickness and Equivalent Normal Residual Stress Distribution A fracture of ceramics occur usually from one of many initial defects existing in ceramics
Summary
Ceramic/metal joint is an excellent technology to carry out the application expansion of the monolithic ceramics, which are brittle materials. “active-metal” brazing method using Ag-Cu-Ti is applied actively to the chamber of the vacuum valve, the semiconductor plate and parts of automobile, and is expected very much as the structural material and the function material. Though this ceramic/metal joints technology is not performed academic proof enough to safety and reliability, has already been used as many joint structure products [1,2]. A major problem in ceramic/metal joints is thermal expansion coefficient mismatch between ceramics and metal. It should be considered that the interlayer thickness has significant influence on the joint strength with considering the residual stress
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